The subject line was “Islam,” and as I clicked on this email chain from Bill, I read on: “Don’t think for a moment that … there haven’t been any Islamic takeovers in American cities. It’s time for border control, or start planning for a very big goodbye to the American way of life. What has already happened to England once they opened their borders without any entry control can happen here.” It’s obvious that “the British have passively succumbed to the Muslim invasion.” We need to keep circulating this email, it said, before it is too late.

I disagree; stop the email in its tracks. London seems to be doing fine with a Muslim mayor. And the “American way of life” is under siege? A complicated question.

This is not the first such email from my old friend in the Midwest; others have decried welfare queens or tried to convince me that President Obama was in fact not an American citizen. How do I respond?

With an edge of disapproval. Using a fact checker to determine the extent of the fiction in the email is easy, and I let Bill know the results. It’s also natural to mention that in our rural Iowa community, we avoided speaking negatively of others. “If you can’t say something nice, don’t say anything at all,” was a sort of moral byword. And I remind him that we, too, came from immigrant families.

The correspondence would usually end here. But this time, Bill shoots back: “Wanted to see how a devout leftie like you would respond to an e-mail such as this. Guess I found out! Figured you would say it was all fiction — better response than I thought! Just wanted to have a little fun.”

At my expense? His taunt stops me cold. And when he adds, “I have no idea who else we knew back in Iowa might be on your side, but I hope not many.” I am speechless.

My friend Sarah advises, “Give it up. There’s no good way to combat this thinking.” I’m tempted.

But the email rankles; it’s like a splinter under my fingernail. What is going on here? Bill and I grew up in a close-knit small town, and our parents were friends. Our long history began when our grandparents arrived in Iowa from Northern Europe in the 1880s and we shared the prevailing myth about the community they had founded, that it was some variety of ideal.

Yet I now wonder, were there things we didn’t see beneath the calm surface of that community? How perfect was it, really? We could be condescending toward people in other small towns around us — with good reason, was the local attitude. Even among the locals, there was a kind of ranking of families and individuals. We were judgmental, with quiet voices.

Besides us, there was another group in town, a small one, of immigrants who had also chosen the rich farmland of Iowa. They were Irish, Catholic and, for the most part, Democrat. We Protestants were discouraged from dating Catholics. “Better not to,” our parents said.

Though subtle, these were indeed biases, as were our attitudes toward blacks and Jews, whom we knew only from a distance. When a black family stopped at a Main Street café now and then, there would be questions about the “incident”: “Where were they coming from?” “Why did they stop here?” And the Jews? I’m embarrassed to say that they were, to us, just the rug sellers and clothing store owners in a city an hour away. Worst of all, we sometimes heard the adults use slurs and ugly expressions when talking about them.

The future harm of off-handedly demeaning outsiders, Catholics, blacks or Jews was never considered, never discussed. And as long as time stood still and people stayed nearby, the damage was limited. But as time sped up and our world opened onto the 1960s, how would we manage?

Bill went to a state university to become a veterinarian and I chose a liberal arts college and majored in English. I know too little about his life and work after college to make trustworthy comparisons between us.

I do know that in his retirement, he and his wife spend summers at their cabin in Minnesota, where Bill is a much-loved fisherman. One spring he told me, “I’m anxious for the season to start. I fish two different lakes every day and I give fish away through my ‘fish for widows ministry.’ They really enjoy the fresh walleye and northern pike.”

That side of Bill I can talk to. It’s when he calls me a “devout leftie” and adds that he only meant to “have a little fun,” that I step back. Our lives took us in different directions, with Bill remaining in the Midwest and me becoming a New Yorker.

Both my nature and my life experiences contributed to my identity, quite a contrast to Bill’s, which emerges in his conclusion. “I have no problem forwarding these messages. I’m just another old conservative white guy who has always worked for everything that I have. I don’t like to see the system abused.” He might as well add, you represent those people undermining the American way of life, as I define it.

Ultimately, Bill and I are emblematic of the many other Americans who today wear ideological blinders in the struggles over national issues that threaten to tear us apart. We each have our identity. We are members of separate groups who can no longer communicate with equanimity across the divide.

Columnists write frequently on these topics. Given the profound effect on me of this email from Bill, I read a lot of them.

In one such essay, after the recent school shooting in Florida, David Brooks, of The New York Times, focuses on “Respect First, Then Gun Control.” He cites a group called Better Angels, which is in the “trust and respect business.” In workshops across the country, its members urge avoiding stereotypes, seeing people as individuals, and practicing respect and empathy. “Better Angels,” wrote Brooks, aims “to build a group of people whose personal bonds with their fellow citizens redefine how they engage in the political system.”

Could the Better Angels approach work for people like Bill and me? Help us find common ground? We need to give it a try, before it’s too late.

Mary K. Otto lives in Norwich.